Mounting structure for cutting blade of dicing apparatus

Abstract: A mounting structure for a cutting blade in a dicing apparatus in which a mounted blade is rotated in a well-balanced condition and further the blade can be easily attached to and detached from the apparatus. The mounting structure of the invention comprises a mount (3) including a first cylindrical engagement portion (31), and a first screw portion (33); a cutting blade (4) including a second engagement portion (43) engaging with a first engagement portion (31); and a screw member (5) including a second screw portion (51) being screwed into the first screw portion (33) so that the screw member (5) presses the cutting blade (4) against the flange surface (32) for fixation, the mount (3) further including a third cylindrical engagement portion (36), and the screw member (5) including a fourth engagement portion (52) engaging with the third engagement portion (36).

Description: The present invention relates to a mounting structure for a cutting blade of a dicing apparatus which conducts narrow-groove cutting and in which a cutting blade, in which abrasive grains made of diamond and other materials are fixed with nickel, is rotated at high speed. A dicing apparatus is used for forming narrow grooves and separating a semiconductor wafer into IC chips (see for example EP-A-0 131 809). The blade of the dicing apparatus is a disk-shaped rotary blade made of abrasive grains of diamond which are fixed with nickel. The thickness of the outer portion of the cutting blade is several tens of microns. This blade is rotated by a spindle motor at high speed so as to cut narrow grooves. Therefore, an end portion of the blade wears away when the grooves are formed. Accordingly, it is necessary to replace the blade in accordance with the processing. For this reason, it is arranged that the blade portion can be attached to and detached from the spindle motor. In the dicing apparatus, the spindle motor is rotated at high speed. Therefore, it is necessary that the spindle motor is well-balanced when the blade is attached to the spindle motor. Consequently, a rotational center of the spindle motor and that of the blade are made to coincide with each other using an engagement structure so that the spindle motor is well-balanced. In the structure in which the blade is mounted, the mount is engaged with the spindle shaft, and then fixed with a nut. In the blade mounting structure described above, all the operator must do is to engage the blade with the mount so as to fix it. Therefore, the blade can be easily replaced. In this case, the accuracy of a position of the center of the blade is determined by the accuracy of an engagement portion of the mount and the blade, and the perpendicularity of the blade with respect to the rotational shaft is determined by the accuracy of the flange and blade surfaces. Therefore, when the machining accuracy of the engagement portions of the flange surface and blade surface is improved, the blade 4 can be accurately attached to the mount. A problem is caused when the workability of the blade detaching operation is improved, which will be described as follows: When the blade is mounted in the manner described above, the rotational balance is determined by an amount of gap of the engaging portion, that is, the rotational balance is determined by a tolerance of the gap. The smaller the tolerance of the engaging portion is reduced, the better the rotational balance is improved. However, in the case where the tolerance of the engagement portion is reduced, it becomes difficult to insert the blade into the mount. In general, a base of the blade is made of aluminum alloy. Therefore, when the blade is inserted canted, an inappropriate contact condition is caused and the engagement portion is damaged, and it becomes impossible to put the blade into practical use. The present invention discloses a mounting structure for a cutting blade in a dicing apparatus comprising: a mount disposed at a fore end of a spindle motor to be rotated at high speed; a cutting blade attached to said mount; and a screw member to fix said cutting blade to said mount, said mount including a first cylindrical engagement portion of which the center coincides with a rotational center; a flange surface perpendicular to a rotational axis; and a first screw portion, said cutting blade including a second engagement portion engaging with said first engagement portion; and a blade surface coming into contact with said flange surface, said screw member including a second screw portion of a screw member is screwed into said first screw portion wherein said cutting blade is mounted onto said mount so that said first engagement portion is engaged with said second engagement portion, and said second screw portion of said screw member is screwed into said first screw portion so that said screw member presses said cutting blade against said flange surface for fixation, and such a structure is characterized in that: when said cutting blade is mounted onto said mount, at a position where an end of said second engagement portion comes into contact with an end of said first engagement portion, in the case where said flange surface and said blade surface are held in parallel, and then, said cutting blade is inclined with respect to said mount by an amount of a gap caused by an engagement tolerance of said first engaging portion and said second engagement portion, a portion of said blade surface comes into contact with said flange surface. In the new blade mounting structure, at a position where the engagement portions are contacted with each other in the case of insertion of the cutting blade, the cutting blade comes into contact with the mount when the cutting blade is inclined by an amount corresponding to a gap formed due to the tolerance of the engagement portion. Accordingly, at the position, there is no possibility that the blade is further inclined, and as a result, the engagement portions are appropriately contacted. In the accompanying drawings:- The present invention will be more clearly understood from the description as set forth below with reference to the accompanying drawings, wherein: Figs. 1A and 1B are views showing the conventional blade mounting structure; and, Figs. 2A, 2B and 2C are schematic diagrams for illustrating a blade mounting structure which is an embodiment of the invention. Before proceeding to a detailed description of the preferred embodiment of the present invention, a prior art blade mounting structure will be described, with reference to the accompanying drawings relating thereto, for a clearer understanding of the differences between the prior art and the present invention. In the accompanying drawings, like or corresponding functional parts are indicated by the same reference characters and repetitive description thereof will be omitted. Figs. 1A and 1B are views showing a conventional structure in which the blade is attached to the spindle of the dicing apparatus. Fig. 1A is a view showing a condition in which the blade is removed, and Fig. 1B is a view showing a condition in which the blade is attached. In Figs. 1A and 1B, reference numeral 1 indicates a main body of a spindle motor; 2 indicates a spindle shaft; 3 indicates a mount for mounting a blade, which is provided at an end of the spindle shaft 2; 4 indicates a blade; and 41 indicates a cutting edge. A blade in which the metal mount is provided with a cutting edge is referred to as a hub blade, however, it will be referred to as a blade in this specification, hereinafter. Reference numeral 5 indicates a nut to fix the blade 4. The mount 3 and blade 4 are respectively provided with engagement portions 31 and 43. When the engagement portion 43 is engaged with the engagement portion 31 of the mount 3, a rotational center of the spindle motor and a center of the blade 4 can be positioned to a tolerance of the engagement portion. A surface 32 coming into contact with the blade 4, the surface being perpendicular to a rotational shaft of the mount 3, is made in such a manner that the surface 32 is accurately perpendicular to the rotational shaft. Also, a surface 42 of the blade 4 coming into contact with the surface 32 of the mount 3 is made in such a manner that the surface 42 is highly accurately perpendicular to the rotational shaft. Under the condition that these surfaces are contacted with each other, the cutting edge of the blade 4 can be set highly accurately perpendicular to the rotational shaft. In this case, the surface 32 of the mount 3 perpendicular to the rotational shaft is referred to as a flange surface, and the surface 42 of the blade 4 perpendicular to the rotational shaft is referred to as a blade surface. Under the condition that the blade 4 is engaged with the mount 3, a screw 51 of the nut 5 is screwed into a screw 33 of the mount 3 so as to be fixed. In the structure shown in Figs. 1A and 1B in which the blade 4 is mounted, the mount 3 is also engaged with the spindle shaft 2, and then fixed with a nut 34. Reference numeral 35 is a screw used for the fixation. Another method for attaching the mount 3 to the spindle shaft 2 is to press-fit the mount 3. When the blade mounting structure shown in Figs. 1A and 1B is adopted, all the operator must do is to engage the blade 4 with the mount 3 so as to fix it. Therefore, the blade 4 can be easily replaced. In this case, the accuracy of a position of the center of the blade 4 is determined by the accuracy of an engagement portion of the mount 3 and the blade 4, and the perpendicularity of the blade 4 with respect to the rotational shaft is determined by the accuracy of the flange and blade surfaces. Therefore, when the machining accuracy of the engagement portion, flange surface and blade surface is high, the blade 4 can be accurately attached to the mount 3. However, as described previously, there is a problem in the blade mounting structure illustrated in Figs. 1A and 1B. The embodiment of Fig. 2 is essentially the same as the conventional one shown in Fig. 1. However, in this case, the tolerance of engagement portions, the thickness of the first engagement portion 31, the height of the first engagement portion 31 from the flange surface, and the diameter of the flange surface are determined for a condition in which the engagement portions are not engaged under an inappropriate contact condition when the blade is inserted into the mount. This condition will be explained as follows. As shown in Fig. 2A, the diameter of the flange surface 32 is DF, the diameter of the first engagement portion 31 is D1, the thickness of the first engagement portion 31 is T, the gap between the flange surface 32 and the first engagement portion 31 is P, and the diameter of the second engagement portion 43 is D2. The difference between D1 and D2 is the tolerance of the engagement portion. The blade 4 is capable of being inclined within a range of the tolerance without causing inappropriate contact with respect to the rotational shaft. When the blade 4 is mounted onto the mount 3 as illustrated in Fig. 2B, the blade 4 is inclined within the range in which the blade 4 can be inclined with respect to the mount 3, under the condition that the fore ends of the engagement portion are contacted. In this case, if a portion of the blade 42 comes into contact with the surface of the flange 32, it is impossible that the blade 42 is further inclined. Accordingly, there is no possibility that an inappropriate contact occurs between the blade and the rotational shaft. Consequently, under the condition that the fore ends of the engagement portions are contacted as illustrated in Fig. 2B, the blade 4 is inclined so that a portion of the blade surface 42 comes into contact with the flange surface 32. This inclination angle may be set to be within the range in which the blade can be inclined at the tolerance of the engagement portion. The inclination angle "a" in Fig. 2B is expressed by the following equation. a = arctan 2(P+T)/(DF+D2) Concerning the angle by which the blade can be inclined to the tolerance of the engagement portion, the following equation is satisfied as shown in Fig. 2C. (T tan  + D1)cos = D2 The above equation is changed into the following equation. Tsin  + D1cos  = D2 When  is sufficiently small in the above equation, the following equation can be obtained.  = arcsin (D2-D1)/T Accordingly, when DF, D1, T, P and D2 are determined so that the above angle "a" can be smaller than this angle , an inappropriate contact may not occur when the blade is inserted. In order to actually realize the above condition, the thickness T of the engagement portion and the gap P between the flange surface 32 and the first engagement portion 31 are reduced as small as possible, and the flange diameter DF is extended. As described above, the inclination of the blade 4 with respect to the rotational shaft is determined by the accuracy of the flange surface 32 and the blade surface 42, and the engagement portion is used only for making the center of the rotational shaft to conform with that of the blade 4. Therefore, even when the thickness T is reduced, no problem is caused except for wear caused when the blade is detached. As explained above, according to the present invention, a blade mounting structure can be realized in which the blade is rotated in a well-balanced condition and further the blade is easily detached.

Claims: A mounting structure for a cutting blade in a dicing apparatus comprising: a mount (3) disposed at a fore end of a spindle motor (1) to be rotated at high speed; a cutting blade (4) attached to said mount (3); and a screw member (5) to fix said cutting blade (4) to said mount (3), said mount (3) including a first cylindrical engagement portion (31) of which the center coincides with a rotational center; a flange surface (32) perpendicular to a rotational axis; and a first screw portion (33), said cutting blade (4) including a second engagement portion (43) engaging with said first engagement portion (31); and a blade surface (42) coming into contact with said flange surface (32), said screw member (5) including a second screw portion (51) of a screw member (5) is screwed into said first screw portion (33), wherein said cutting blade (4) is mounted onto said mount (3) so that said first engagement portion (31) is engaged with said second engagement portion (43), and said second screw portion (51) of said screw member (5) is screwed into said first screw portion (33) so that said screw member (5) presses said cutting blade (4) against said flange surface (32) for fixation, characterized in that: when said cutting blade (4) is mounted onto said mount (3), at a position where an end of said second engagement portion (43) comes into contact with an end of said first engagement portion (31), in the case where said flange surface (32) and said blade surface (42) are held in parallel, and then, said cutting blade (4) is inclined with respect to said mount (3) by an amount of a gap caused by an engagement tolerance of said first engaging portion (31) and said second engagement portion (43), a portion of said blade surface (42) comes into contact with said flange surface (32).

Inventors: CHIBA KIYOTAKA, TSUCHISHIMA JIRO, CHIBA, KIYOTAKA, TSUCHISHIMA, JIRO, CHIBA, KIYOTAKA, C/O TOKYO SEIMITSU CO., LTD., TSUCHISHIMA, JIRO, C/O TOKYO SEIMITSU CO., LTD.
Applicants: TOKYO SEIMITSU CO LTD, TOKYO SEIMITSU CO.,LTD.
Application year: 1994
Main classification: B23D61
IPC codes: H01L21, B26D7, B24B45, B23D61, B24D5